Subterranean boring machines are used to install a pipe comprised of multiple casing sections or a similar product in the ground without excavating a trench for the pipe. Some boring machines are used to bore a generally horizontal hole and to install a plurality of pipe sections therein between a generally vertical launch shaft or pit and a similarly oriented target shaft or pit. The launch shaft or pit is excavated to a depth to permit the boring machine to be placed in alignment and on grade with the desired underground installation. Boring machines that are commonly placed in such launch pits generally include a track that is located at the bottom of the launch pit and oriented along the desired boring direction, and a carriage that rolls or otherwise travels along the track. The carriage includes a pusher mechanism that is adapted to move the carriage along the track between a start point and a terminal point, and a rotational mechanism that is adapted to rotate a tool carried by the boring machine.
In some conventional boring machines, a pilot hole is first bored along the centerline of the intended product bore. Some such machines use a small pilot head having an inclined face at its leading end. Typically, the pilot system will include a hollow casing, and the pilot head will include an illuminated target on its trailing end. A theodolite mounted at a fixed position in the launch pit apart from the boring machine is aligned so that an operator can view the position of the illuminated target on the pilot head with respect to the cross-hairs of the theodolite. The first section of the pilot casing and the pilot head are pushed into the ground in the boring direction by the pusher mechanism without rotating the pilot head. However, because the inclined face on the pilot head gives rise to a reaction force exerted by the soil through which the head moves, rotation of the head as it is pushed in the boring direction may be required to keep the head on the desired course, as indicated by the position of the target with respect to the cross-hairs of the theodolite. When the carriage reaches the terminal point of the track, the pilot head is disengaged and the carriage is withdrawn to the start point. Multiple sections of pilot casing are added, one by one, to the end of the pilot string and pushed by the pusher mechanism until the pilot head reaches the target pit. After the pilot hole is completed, a boring assembly having an outer diameter that corresponds to the outer diameter of the product casing to be installed is selected. This boring assembly, which comprises a support casing with a cutter head at the leading end and an internal material removal auger or other conveyor located behind the cutter head, is lowered into the launch pit and mounted on the carriage. The boring assembly is attached to the rear end of the pilot casing and aligned with the pilot hole. As the carriage is then pushed or driven along the track following the pilot line, the cutter head is operated to bore a hole centered on the pilot bore, and the conveyor is operated to carry the cuttings back towards the launch pit. A plurality of spoil paddles located in a front section of the carriage sweep the cuttings out of the boring machine and into the launch pit through openings provided for that purpose. When the carriage reaches the terminal point of the track, the support casing and internal conveyor are disengaged and the carriage is retracted to the start point. The pilot head is removed from the pilot casing string in the target pit, and an additional section of support casing with an internal conveyor section is mounted to the carriage and attached to the casing and conveyor sections that were disengaged from the carriage. Then the carriage is engaged to drive the support casing further in the boring direction while operating the cutter head and the internal conveyor. Multiple sections of this cutting assembly are added, and the pilot system is removed, piece by piece, from the target pit, until the cutter head reaches the target pit. Then the support casing and conveyor sections are removed, one by one, as product pipe sections of the same outer diameter as the boring assembly are pushed by the carriage into the bore.
A variation on this type of guidance system is offered by the Bohrtec subsidiary of Herrenknecht in a machine which may be used for small-diameter tunnels and does not require the formation of a pilot bore. The Bohrtec machine employs a boring assembly, carriage and track such as is employed by conventional machines that use a pilot bore, as well as an optical guidance system that employs a theodolite mounted at a fixed position in the launch pit apart from the boring machine. The theodolite is aligned so that an operator can view the position of an illuminated target on the back of the cutter head through the hollow shaft of an auger conveyor. The cutter head on the Bohrtec machine is mounted to a steering module that is selected to match the diameter of the product casing to be installed. The steering module is attached to a first support casing having a hollow internal auger in such a way that the operator can tilt the steering module with respect to the first support casing (as in conventional tilt steering systems), thereby steering by ground reaction forces as the support casing, steering module and cutter head are pushed by the carriage into the ground along the desired bore path. Cuttings cut by the cutter head are carried by the internal auger through the support casing back to the launch pit. When the carriage reaches the terminal point of the track, the support casing and internal conveyor are disengaged and the carriage is retracted to the start point. An additional section of support casing with an internal auger conveyor section is mounted to the carriage and attached to the support casing and conveyor sections that were disengaged from the carriage. Then the carriage is engaged to drive the steering module and support casing further in the boring direction while operating the cutter head and the internal conveyor. Multiple sections of this cutting assembly are added until the steering module reaches the target pit. Then the support casing and conveyor sections are removed, one by one, as product pipe sections of the same outer diameter are pushed by the carriage into the bore.
Some boring machines employ a laser guidance system that directs a laser beam through a component of the boring machine to a target located behind the cutter head. One such system is described in U.S. Pat. No. 3,321,248. According to this patent, a laser generator is mounted within the launch pit and arranged to direct its beam in a direction that is parallel to the boring axis of the machine. Two identical targets are mounted on the boring machine, one at the forward end behind the cutter head, and the other at the rear end. Each target comprises a plate of transparent or translucent material that is provided with grid lines, and each is mounted so that its grid lines are aligned with those of the other. When the laser beam impinges both targets at the same point with respect to the grid lines, the machine will be on course. If the laser beam does not impinge both targets at the same point, appropriate correction can be made in the boring direction by steering the machine.
U.S. Pat. No. 3,517,966 describes a laser guidance system for a boring machine which includes a sighting device comprising a luminous cross that is mounted behind the cutter head. In one embodiment of the guidance system, the image of the luminous cross is directed by a pair of mirrors disposed at 45° angles on either side of the boring axis to generate a virtual luminous cross in the plane of the cutter head. In another embodiment of this system, a laser located behind the machine directs light in the desired boring direction; however, this light is redirected by a pair of mirrors disposed at 45° angles on either side of the boring axis to impinge on a target point of a sighting device located behind the cutter head. By steering the boring machine so that the laser beam remains on the target point, its cutter head will be directed in the desired boring direction.
Another laser guidance system is described in U.S. Pat. No. 4,142,763. According to this patent, a laser generator is mounted in a tunnel retaining wall at the rear of a shield-type boring machine so that its beam is directed in the boring direction. A laser detector is mounted in the shield body for receiving the beam and for determining if the boring machine is proceeding on course. The laser detector includes an X-Y scanning type receiver having a transparent plate with a central aperture through which the beam may pass when the boring machine is on course. A gyroscopic device is attached to the opposite side of the scanning receiver along with a rolling angular detection device. The detector is mounted on a vertical threaded rod which may be rotated by a first motor to raise or lower the detector. A coupling member at the upper end of the vertical rod is attached to a horizontal threaded rod which may be rotated by a second motor to move the detector in horizontal directions along the horizontal rod. Potentiometers are attached to the threaded rods that produce voltage signals corresponding to revolutions of the rods so that the relative vertical and horizontal positions of the laser detector can be determined. The detector also includes photoelectric elements that enable the detector to determine the vertical and horizontal position of the laser beam on the receiver if it is out of alignment with the central aperture. The gyroscopic device attached to the side of the detector opposite the laser source includes lenses and electronics that can generate a signal when there is a deviation of the laser beam from that of the desired pitch and angular orientation of the shield machine. If the shield machine is off course, the propelling jacks can be selectively operated to return the machine to its proper course.
U.S. Pat. No. 5,361,854 describes a boring machine which includes at least three measuring units, each of which comprises a pair of lasers mounted back to back so that the laser beams are projected in opposite directions. Each measuring unit is mounted on the rear end of a product casing, and each includes a pair of targets, one at each end. The measuring units are mounted on adjacent product casings so that the first beam of a measuring unit impinges on the second target of an adjacent measuring unit located in one direction and the second beam of the measuring unit impinges on the first target of a measuring unit located in the opposite direction. Each target includes a photo array of light sensing elements for detecting the point of impingement of the laser beam on the target. A processor receives information about the impingement of the laser beams on the targets and calculates the direction of the bore being produced by the machine so that the steering head can be steered in the desired direction.
International Patent Publication No. WO 96/06264 describes an auger boring machine having a cutter head that includes an elongated tube portion which is supported by roller bearings within an outer pipe section. A target is mounted on the rear end of the tube portion of the cutter head. A support casing with an internal auger having a hollow shaft is mounted onto the rear end of the tube portion, so that material cut by the cutter head is carried back by the auger to a discharge point. The rear end of the hollow shaft of the auger is supported by a collar which includes a sight glass. A laser mounted behind the machine is adapted to direct a laser beam through the hollow auger to the target mounted on the rear end of the tube portion of the cutter head. A sensor rotates with the target and closes a circuit to permit laser activation only when the sensor is in the 6:00 o'clock position. If the laser beam hits the target off center, a steering system may be activated to re-align the cutter head.
U.S. Patent Publication No. 2009/0152012 describes a slurry-style microdrilling machine intended for drilling bores for pipes having diameters of 600 mm or less using a rotating cutter head assisted by ejecting pressurized fluid. This machine includes a laser guidance system and a back reamer that essentially allows for drilling of a pilot hole of a uniform diameter, followed by back reaming to enlarge the bore hole to any of several diameters. The pilot hole position is monitored by means of a laser set at the origin of the bore hole which is directed through a laser sight cavity to indicate a position on a target mounted on the cutter head.
Notes on Construction
The use of the terms “a”, “an”, “the” and similar terms in the context of describing the invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising”, “having”, “including” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The terms “substantially”, “generally” and other words of degree are relative modifiers intended to indicate permissible variation from the characteristic so modified. The use of such terms in describing a physical or functional characteristic of the invention is not intended to limit such characteristic to the absolute value which the term modifies, but rather to provide an approximation of the value of such physical or functional characteristic. All methods described herein can be performed in any suitable order unless otherwise specified herein or clearly indicated by context.
The use of any and all examples or exemplary language (e.g., “such as”) herein is intended merely to better illuminate the invention and not to place a limitation on the scope of the invention, unless otherwise indicated by the claims. Nothing in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Various terms are specifically defined herein. These terms are to be given their broadest possible construction consistent with such definitions, as follows:
The term “boring direction”, when used in describing the operation of a boring machine or the relative position of a component of a boring machine, refers to the direction of advance of the cutter head of the machine as the boring operation is carried out.
The terms “front” and “front end” of the boring machine refer to the end of the machine that leads in the boring direction. When referring to a component of the boring machine, the terms “front” and “front end” refer to that portion of the component that is nearer the front end of the boring machine.
The terms “rear” and “rear end” of the boring machine refer to the end opposite the front end. When referring to a component of the boring machine, the terms “rear” and “rear end” refer to that portion of the component that is nearer the rear end of the boring machine.
The terms “forward” and “in front of”, as used herein to describe a relative position or direction on or in connection with a boring machine, refer to a relative position towards the front end of the machine or towards the boring direction.
The terms “rearward”, “behind” and “rearwardly”, as used herein to describe a relative position or direction on or in connection with a boring machine, refer to a relative position or direction towards the rear end of the machine or opposite the boring direction.
The term “linear actuator” refers to an electric, hydraulic or electro-hydraulic device that generates force which is directed in a straight line. One common example of a “linear actuator” is a hydraulic actuator which includes a cylinder, a piston within the cylinder, and a rod attached to the piston. By increasing the pressure within the cylinder on one side of the piston (over that on the opposite side of the piston), the rod will extend from the cylinder or retract into the cylinder.
The terms “product casing”, “product casing component”, “product casing section” and similar terms refer to a section of pipe or other product that is installed or intended to be installed in a bore. The term “product casing” may also refer to a plurality of sections of pipe or other product or product casing components that are joined, or intended to be joined, together. The term “differently-sized product casings” refers to product casings having different inside diameters and/or outside diameters. The terms “a selected one of the product casings”, “selected product casings” and similar terms refer to a product casing having an inside diameter that is selected for installation within a particular bore. The term “corresponds” and similar terms, when used to compare a diameter or other dimension of a component of the auger boring machine with a similar dimension of “a selected one of the product casings”, refers to the suitability of the component having such dimension for use in installing the “selected one of the product casings”.
The terms “internal casing”, “internal casing component”, “internal casing section” and similar terms refer to a section of the portion of the boring machine that is adapted to include an auger section which is adapted to rotate with respect to the internal casing. The term “internal casing” may also refer to a plurality of sections of internal casing or internal casing components that are joined, or intended to be joined, together.